1. Field of the Invention
The present invention relates to an injection apparatus for industrial machines such as plastic injection molding machine or die casting machine, specifically to the injection apparatus capable of molding an article with high quality by improving injection speed thereof.
2. Description of Related Art
The quality of a molded article is affected by the injection speed and pressure during injecting and filling in the industrial machine in which the mold material, such as melt resin or metal, is injected and filled into a the cavity formed within a mold die of the machine.
Incidentally, the cavity shape in the mold die is may be of various kinds, in accordance with the mold articles. As such, the function and capability of the injection speed, pressure, etc. required by the injection apparatus greatly vary.
On the other hand, because of the requirement for noiseless, cleanliness, good controllability, and spread of powerful servomotor for several years, demand for the industrial machine from a hydraulic drive system to an electric drive system has been rapidly changing.
An injection apparatus for injection molding machine of the type with the electric drive system is provided with a screw supported having one end capable of rotating to supply resin melt and kneaded in the barrel to the mold die(cavity). A support member of the screw is capable of linear movement by means of linear guides.
A drive force is supplied to the support member, which is generated by converting rotational movement of an electric motor as a drive source to linear movement using a pair of ball screw and ball nut arrangement.
There are two methods for the conversion. One method is a ball nut-drive method, and the other method is a ball screw-drive method. In the ball nut-drive method, the support member is connected to the ball screw engaging with the ball nut. The ball nut is may be rotated by the electric motor directly or may be indirectly coupled to it. In the ball screw-drive method, the support member is connected to the ball nut engaging with the ball screw. The ball screw is may be rotated by the electric motor directly or may be indirectly coupled to it.
Besides the ball screw and ball nut arrangement, there exists an injection apparatus with the support member connected to a mechanism in which a linear movement is produced through a drive force generated by electromagnetic force like a linear motor, or with a plunger instead of the screw.
Even in such injection apparatus for injection molding machine of the type with the electric drive system, there still exists limits as to the requirement for a high speed injection capable of molding the mold material mentioned above while still producing a high quality molded article.